Linear/rotary electromagnetic device

ABSTRACT

In a preferred embodiment, a linear/rotary electromagnetic device, including: a housing ( 20 ); first and second stators ( 22  and  40 ) disposed in the housing, first and second rotors ( 24/26  and  42/44 ) disposed in the housing and magnetically interacting, respectively, with the first and second stators; the first stator and the first rotor comprising a rotary motor; the second stator and the second rotor comprising an electromagnetic brake; a shaft ( 28 ) extending through a portion of the housing and axially through the first and second rotors, the shaft having a threaded portion ( 50 ) extending through a complementary threaded portion ( 44 ) of one of the first and second rotors; whereby; when the electromagnetic brake is locked and the rotary motor is rotated in a first direction, the shaft will move axially in a first direction; when the electromagnetic brake is locked and the rotary motor is rotated in the second direction, the shaft will move axially in a second direction; and when the electromagnetic brake is released and the rotary motor is rotated, the shaft will rotate with the rotary motor.

This application is a 371 of PCT/US98/17801 filed Aug. 27, 1998, whichclaims benefit of Provisional No. 60/057,683 filed Aug. 27, 1997.

TECHNICAL FIELD

The present invention relates to electromagnetic devices generally and,more particularly, but not by way of limitation, to a novelelectromagnetic device which selectively provides rotary and/or linearmotion at a single output shaft.

BACKGROUND ART

In certain applications, it is desirable to have a shaft which mayselectively rotate and/or reciprocate. Such an application, for example,is in the robotic picking and placing of components where it may berequired to axially move a component to an insertion position and thenrotate the component to screw it in place. Conventional motorarrangements to accomplish such motion are often complicated and heavy,a substantial disadvantage for robotics applications. Another type ofapplication requiring a shaft which may selectively rotate and/orreciprocate is in the precise control of laparoscopic and other suchmedical instruments.

In either type of application, it is frequently required that the linearmotion be locked while rotary motion takes place. For a rotary/linearmotor, this makes it desirable that the linear and rotary motions becontrollable independently of one another.

Accordingly, it is a principal object of the present invention toprovide an electromagnetic device which selectively provides both linearand/or rotary motion at a single output shaft.

It is an additional object of the invention to provide such anelectromagnetic device in which linear and rotary motions arecontrollable independently of one another.

It is another object of the invention to provide such an electromagneticdevice in which linear motion can be locked while rotary motion isprovided.

It is a further object of the invention to provide such anelectromagnetic device that is simple and economical to manufacture.

An additional object of the invention is to provide such anelectromagnetic device that is lightweight and compact.

Other objects of the present invention, as well as particular features,elements, and advantages thereof, will be elucidated in, or be apparentfrom, the following description and the accompanying drawing figures.

DISCLOSURE OF INVENTION

The present invention achieves the above objects, among others, byproviding, in a preferred embodiment, a linear/rotary electromagneticdevice, comprising: a housing; first and second stators disposed in saidhousing; first and second rotors disposed in said housing andmagnetically interacting, respectively, with said first and secondstators; said first stator and said first rotor comprising a rotarymotor; said second stator and said second rotor comprising anelectromagnetic brake; a shaft extending through a portion of saidhousing and axially through said first and second rotors, said shafthaving a threaded portion extending through a complementarily threadedportion of one of said first and second rotors; whereby; when saidelectromagnetic brake is locked and said rotary motor is rotated in afirst direction, said shaft will move axially in a first direction; whensaid electromagnetic brake is locked and said rotary motor is rotated ina second direction; and when said electromagnetic brake is released andsaid rotary motor is rotated, said shaft will rotate with said rotarymotor.

BRIEF DESCRIPTION OF DRAWINGS

Understanding of the present invention and the various aspects thereofwill be facilitated by reference to the accompanying drawing figures,submitted for purposes of illustration only and not intended to definethe scope of the invention, on which:

FIG. 1 is a side elevational view, partially in cross-section andpartially cut-away, of an electromagnetic device according to a firstembodiment of the present invention.

FIG. 2 is a side elevational view, partially in cross-section andpartially cut-away, of an electromagnetic device according to a secondembodiment of the present invention.

FIG. 3 is a side elevational view, partially in cross-section andpartially cut-away, of an electromagnetic device according to a thirdembodiment of the present invention.

FIG. 4 is a side elevational view, partially in cross-section andpartially cut-away, of an electromagnetic device according to a fourthembodiment of the present invention.

BEST MODE OF CARRYING OUT THE INVENTION

Reference should now be made to the drawing figures, on which similar oridentical elements are given consistent identifying numerals throughoutthe various figures thereof, and on which parenthetical references tofigure numbers direct the reader to the view(s) on which the element(s)being described is (are) best seen, although the element(s) may be seenalso on other views.

FIG. 1 illustrates a linear/rotary electric motor, constructed accordingto a first embodiment of the present invention, the motor beinggenerally indicated by the reference numeral 10. Motor 10 includes ahousing 20 having an annular stator structure 22 fixedly mounted thereinin magnetic interacting relationship with an annular permanent magnet 24fixedly mounted on an annular bushing 26, the latter two elementscomprising a motor rotor. A shaft 28 extends coaxially through housing20 and includes a cylindrical portion 30 extending coaxially throughbushing 26. Shaft 28 is secured against rotation relative to bushing 26by means of a pin 32 extending through and fixedly attached to thebushing and extending through cylindrical portion 30. To permit axialmovement of shaft 28 relative to bushing 26, pin 32 extends through anaxially extending slot 36 defined through bushing 26.

Housing 20 also includes fixedly mounted therein a second annular stator40 magnetically interacting with an annular permanent magnet 42 fixedlymounted on an annular, internally threaded nut 44, the second stator andthe permanent magnet comprising an electromagnetic brake. A threadedportion 50 of shaft 28 extends through nut 44, the threaded portion andthe internal threads of nut 44 being complementary. An annular permanentmagnet 56 is fixedly mounted on shaft 28 and magnetically interacts witha Hall cell or similar sensor 58 fixedly mounted in housing 20.

In use, initially as rotor 24/26 rotates in one direction andelectromagnetic brake 40/42 is locked by means of applying electricalcurrent to stator 40, shaft 28 will move axially to the left on FIG. 1,while rotating, by virtue of the complementarily threaded portions ofnut 44 and shaft portion 50. When the maximum extent of linear motion ofshaft 28 is reached, magnet 56 triggers Hall cell 58 and brake 40/42 isreleased. With brake 40/42 released, further motion of shaft 28 ispurely rotary. When it is desired to return to the home position shownon FIG. 1, brake 40/42 is locked and rotation of rotor 24/26 in theopposite direction causes shaft 28 to move to the right on FIG. 1 whilerotating.

Bearings 70 and 72 provide axial and radial support for shaft 28 andwires 74 are provided for connection between control means (not shown)and the electrical elements of motor 20.

FIG. 2 illustrates a linear/rotary electric motor constructed accordingto a second embodiment of the present invention, the motor beinggenerally indicated by the reference numeral 80. Motor 80 includes ahousing 90 having an annular stator structure 92 fixedly mounted thereinin magnetic interacting relationship with an annular permanent magnet 94fixedly mounted on an annular, internally threaded bushing 96, thelatter two elements comprising a motor rotor.

Housing 90 also includes fixedly mounted therein a second annular stator100 magnetically interacting with an annular permanent magnet 102fixedly mounted on an annular bushing 104, the second stator and thepermanent magnet comprising an electromagnetic brake. A shaft 98 extendscoaxially through housing 90 and includes a cylindrical portion 110extending coaxially through bushing 104. Shaft 98 is secured againstrotation relative to bushing 104 by means of a pin 116 extending throughthe bushing and through and fixedly attached to cylindrical portion 110.To permit axial movement of shaft 98 relative to bushing 104, pin 116extends through an axially extending slot 118 defined through bushing104.

A threaded portion 120 of shaft 98 extends through bushing 96, threadedportion 120 and the internal threads of the bushing being complementary.An annular permanent magnet 130 is fixedly mounted on shaft 98 andmagnetically interacts with a Hall cell or similar sensor 132.

Bearings 140 and 142 provide axial and radial support for shaft 98 andwires 144 are provided for connection between control means (not shown)and the electrical elements of motor 80.

In use for linear motion, as rotor 94/96 rotates in one direction andelectromagnetic brake 100/102 is locked, shaft 98 will move axially tothe left on FIG. 2, without rotation of the shaft. When the maximumextent of linear motion of shaft 98 is reached, magnet 130 triggers Hallcell 132, brake 100/102 is released, and the motion of the shaft ispurely rotary. Further linear motion of shaft 98 is prevented by virtueof the ends of pin 116 engaging the ends of slot 118. When it is desiredto return to the home position shown on FIG. 2, brake 100/102 is lockedand rotation of rotor 94/96 in the opposite direction moves shaft 98 tothe right on FIG. 2.

FIG. 3 illustrates a linear/rotary electric motor, constructed accordingto a third embodiment of the present invention, the motor beinggenerally indicated by the reference numeral 20′. Since motor 20′ is avariation of motor 20 (FIG. 1), the common elements thereof are givenprimed reference numerals and reference should be made to FIG. 1 for adescription of the elements and the operation thereof to the extent notdescribed with reference to FIG. 3.

The differences between motor 20 and motor 20′ is that, in the latter,permanent magnet 56 (FIG. 1) has been eliminated and Hall cell 58 istriggered when approached by permanent magnet 24′ of rotor 24′/26′.Also, motor 20′ includes a return spring 150 disposed between bushing26′ and bearing 70′ to return shaft 28′ to its home position. Returnspring 150 may not be required if motor 20′ is operating in a verticalposition.

FIG. 4 illustrates a linear/rotary electric motor, constructed accordingto a fourth embodiment of the present invention, the motor beinggenerally indicated by the reference numeral 80′. Since motor 80′ is avariation of motor 80 (FIG. 2), common elements thereof are given primedreference numerals and reference should be made to FIG. 2 for adescription of the elements and the operation thereof to the extent notdescribed with reference to FIG. 4.

A first difference between motor 80 and motor 80′ is that a bushing 160has been disposed between permanent magnet 94′ and threaded bushing 96′to provide centering support for shaft 98′ as shown. Second, permanentmagnet 130 and Hall cell 132 (FIG. 2) have been eliminated and controls(not shown) are relied upon for determining the timing of the lockingand unlocking of brake 100′/102′ and the rotating of rotor 94′/160/96′.An fixed annular flange 162 has been provided on shaft 98′ to engagebushing 104′ at the end of linear movement to prevent further linearmovement during rotation of the shaft. Third, pin 116 and slot 118 (FIG.2) have been eliminated and replaced with a hexagonal shaped portion 166of shaft 98′ to prevent relative rotational motion of the shaft andbushing 104′, the latter being provided with a complementary hexagonalshaped channel axially defined therethrough.

All patent applications, patents, and other documents cited herein areincorporated in their entirety by reference hereinto.

In the embodiments of the present invention described above, it will berecognized that individual elements and/or features thereof are notnecessarily limited to a particular embodiment but, where applicable,are interchangeable and can be used in any selected embodiment eventhough such may not be specifically shown.

Terms such as “upper”, “lower”, “inner”, “outer”, “inwardly”,“outwardly”, and the like, when used herein, refer to the positions ofthe respective elements shown on the accompanying drawing figures andthe present invention is not necessarily limited to such positions.

It will thus be seen that the objects set forth above, among thoseelucidated in, or made apparent from, the preceding description, areefficiently attained and, since certain changes may be made in the aboveconstruction without departing from the scope of the invention, it isintended that all matter contained in the above description or shown onthe accompanying drawing figures shall be interpreted as illustrativeonly and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:
 1. A linear/rotary electromagnetic device,comprising: (a) a housing; (b) first and second stators disposed in saidhousing; (c) first and second rotors disposed in said housing andmagnetically interacting, respectively, with said first and secondstators; (d) said first stator and said first rotor comprising a rotarymotor; (e) said second stator and said second rotor comprising anelectromagnetic brake; (f) a shaft extending through a portion of saidhousing and axially through said first and second rotors, said shafthaving a threaded portion extending through a complementarily threadedportion of one of said first and second rotors; whereby; (g) when saidelectromagnetic brake is locked and said rotary motor is rotated in afirst direction, said shaft will move axially in a first direction; (h)when said electromagnetic brake is locked and said rotary motor isrotated in a second direction, said shaft will move axially in a seconddirection; and (i) when said electromagnetic brake is released and saidrotary motor is rotated, said shaft will rotate with said rotary motor.2. A linear/rotary motor, as defined in claim 1, wherein: said threadedportion is within said first rotor.
 3. A linear/rotary motor, as definedin claim 1, wherein: said threaded portion is within said second rotor.4. A linear/rotary motor, as defined in claim 1, wherein: a portion ofsaid shaft passing through an unthreaded one of said first and secondrotors is attached to said unthreaded one of said first and secondrotors by attachment means which permits relative axial movement of saidportion of said shaft and said unthreaded one of said first and secondrotors but prohibits relative radial movement of said portion of saidshaft and said unthreaded one of said first and second rotors.
 5. Alinear/rotary motor, as defined in claim 4, wherein: said attachmentmeans comprises a pin extending radially through said portion of saidshaft and said unthreaded one of said first and second rotors andfixedly attached to said portion of said shaft, with said pin moveablewithin at an axial slot defined in said unthreaded one of said first andsecond rotors.
 6. A linear/rotary motor, as defined in claim 4, wherein:said attachment means comprises said portion of said shaft having anhexagonal cross section and a channel defined through said unthreadedone of said first and second rotors having a complementarily shapedcross section.
 7. A linear/rotary motor, as defined in claim 1, furthercomprising: a magnetic sensing element fixedly disposed in said housingto sense when said shaft has reached a maximum axial distance of traveland to thereby cause unlocking of said electromagnetic brake.
 8. Alinear/rotary motor, as defined in claim 7, wherein: said magneticsensing element is responsive to a magnet fixedly disposed on said shaftapproaching said magnetic sensing element.
 9. A linear/rotary motor, asdefined in claim 7, wherein: said magnetic sensing element is responsiveto a magnet disposed on said one of said first and second rotorsapproaching said magnetic sensing element.
 10. A linear/rotary motor, asdefined in claim 1, wherein: axial movement of said shaft is terminatedby a flange formed on said shaft engaging an element in saidlinear/rotary motor.